1. Field of the Invention
The present invention relates to laser scanning optics for scanning a laser beam and a laser scanning method using the same. More particularly, the present invention relates to laser scanning optics feasible for, e.g., a thermal transfer system that thermally transfers the pattern of a color filter or an EL (electroluminescence) material to a substrate, and a laser scanning method using the same.
2. Description of the Background Art
Laser scanning optics has customarily been applied to a thermal transfer system mentioned above and a laser printer or similar electrophotographic image forming apparatus for forming a latent image on a photoconductive element. Laser scanning optics for this kind of application is used to form text and graphic images, which are recognizable by eye, and therefor not sufficient for a transfer system of the type needing highly accurate resolution and linearity. Transfer systems of this type include a system for transferring the color filter of a liquid crystal display panel and a display system using EL devices. While optics included in such systems is configured to correct errors in the configuration of a deflector, it cannot reduce the influence of, e.g., a stage.
The conventional laser scanning optics described above scans a laser beam in only one direction. Therefore, the linearity of a line drawn by scanning depends on the accuracy of a deflector and that of optics. This brings about a problem that the bending and waving of a scanning line cannot be corrected.
Moreover, because the laser beam is steered in only one direction, the light intensity distribution of the laser beam is not flat in the direction (subscanning direction) perpendicular to the scanning direction (main scanning direction). More specifically, the light intensity distribution is a Gaussian distribution or a distribution close to it dependent on the intensity distribution of the beam. Consequently, in a laser scanning type of thermal transfer system, the non-uniform light intensity distribution in the subscanning direction directly translates into a non-uniform thermal energy distribution, resulting in irregular transfer.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 58-137738, Japanese Patent Publication No. 63-25550, Japanese Patent Laid-Open Publication No. 2000-66161, and Japanese Patent Nos. 2,783,328 and 2,984,635.
It is an object of the present invention to provide laser scanning optics capable of correcting the bending and waving or a scanning line to thereby insure accurate linearity in the main scanning direction, and providing the light intensity distribution of a laser beam with a flat top to thereby obviate irregular transfer, and a laser scanning method using the same.
In accordance with the present invention, laser scanning optics for scanning a laser beam issuing from a laser in the main scanning direction while repeatedly steering it in the subscanning direction includes focusing optics for focusing the laser beam, a first deflector for steering the laser beam in the subscanning direction, and a second deflector for steering the laser beam in the main scanning direction. The focusing optics causes the laser beam to form an elliptical beam spot, which is elongate in the main scanning direction, in a scanning plane. The first deflector is driven such that the laser beam is scanned at a higher speed in the subscanning direction than in the main scanning direction. The first deflector is so control led, based on a value input beforehand or data measured beforehand, as to correct the distortion of linearity in the main scanning direction by subscanning.
A laser scanning method using the above laser scanning optics is also disclosed.